> ## Documentation Index > Fetch the complete documentation index at: https://veniceai-docs-revamp.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # X402 Top Up > Top up your Venice credit balance using a `PAYMENT-SIGNATURE` header (the legacy `X-402-Payment` and `X-PAYMENT` header names are also accepted). If the header is missing, the endpoint returns payment requirements. This is the primary x402 payment endpoint. It currently returns Base and Solana USDC payment options in the `accepts` array. All inference endpoints (chat, image, audio, video) consume from the credit balance you establish here. ## OpenAPI ````yaml POST /x402/top-up openapi: 3.0.0 info: description: The Venice.ai API. termsOfService: https://venice.ai/legal/tos title: Venice.ai API version: '20260616.154934' x-guidance: >- Venice.ai is an OpenAI-compatible inference API supporting text, image, audio, and video generation. **Authentication options:** - API Key: Use Bearer token in Authorization header - x402 Wallet: Use USDC credits via EVM or Solana wallet (no account required) **For x402 wallet access:** 1. POST /x402/top-up without headers to get payment requirements 2. Choose one of the returned Base or Solana payment options and sign a USDC payment using the x402 SDK 3. POST /x402/top-up with PAYMENT-SIGNATURE header to add credits 4. Call any inference endpoint with SIGN-IN-WITH-X header **Pricing:** Prepaid credits consumed per request. Check /models for available models and their capabilities. servers: - url: https://api.venice.ai/api/v1 security: - BearerAuth: [] tags: - description: >- Generate speech/audio, transcribe audio, and manage asynchronous audio generation jobs. name: Audio - description: >- Given a list of messages comprising a conversation, the model will return a response. Supports multimodal inputs including text, images, audio (input_audio), and video (video_url) for compatible models. name: Chat - description: List and describe the various models available in the API. name: Models - description: Generate and manipulate images using AI models. name: Image - description: Generate videos using AI models. name: Video - description: List and retrieve character information for use in completions. name: Characters - description: >- Billing and usage analytics. **Beta**: This API is currently in beta and may be unstable. Endpoints, request/response schemas, and behavior may change without notice. name: Billing - description: Proxy JSON-RPC requests to blockchain nodes. Billed per credit. name: Crypto RPC - description: >- Wallet-based API access using the x402 protocol. No API key required — authenticate with an EVM or Solana wallet. **How it works:** 1. **Authenticate** — Send a `SIGN-IN-WITH-X` header (base64-encoded signed SIWX payload) with any request. EVM wallets sign an EIP-4361 SIWE message; Solana wallets sign the Solana SIWX message with Ed25519. See the `siwx` security scheme for the exact format. 2. **Top up** — `POST /x402/top-up` without a payment header returns an `accepts` array with Base and Solana USDC payment options. Choose one entry, sign it using the x402 SDK (`npm install x402`), and re-submit with the `PAYMENT-SIGNATURE` header (the legacy `X-402-Payment` and `X-PAYMENT` names are also accepted). 3. **Use any endpoint** — All inference endpoints (chat, image, audio, video, embeddings) accept `siwx` as an alternative to `BearerAuth`. Charges are deducted from your USDC credit balance. 4. **Monitor balance** — `GET /x402/balance/{walletAddress}` returns your current balance. The `X-Balance-Remaining` response header on inference calls also reports it. **Quick start (5 lines):** ``` import { VeniceClient } from '@venice-ai/x402-client' const venice = new VeniceClient(process.env.WALLET_KEY) await venice.topUp(10) // $10 USDC on a supported x402 rail const res = await venice.chat({ model: 'zai-org-glm-5-1', messages: [{ role: 'user', content: 'Hello!' }] }) ``` **Payment:** USDC on Base (chain ID 8453) or Solana mainnet. Minimum top-up: $5. Alternatively, stake DIEM tokens for daily credits (1 DIEM = $1/day). name: x402 externalDocs: description: Venice.ai API documentation url: https://docs.venice.ai paths: /x402/top-up: post: tags: - x402 summary: /api/v1/x402/top-up description: >- Top up your Venice credit balance using a `PAYMENT-SIGNATURE` header (the legacy `X-402-Payment` and `X-PAYMENT` header names are also accepted). If the header is missing, the endpoint returns payment requirements. This is the primary x402 payment endpoint. It currently returns Base and Solana USDC payment options in the `accepts` array. All inference endpoints (chat, image, audio, video) consume from the credit balance you establish here. operationId: topUpX402Balance parameters: - description: >- Signed x402 v2 payment payload (base64-encoded `PaymentPayload`) used to top up the wallet balance on a supported rail such as Base or Solana. The canonical header is `PAYMENT-SIGNATURE`; the `X-402-Payment` and `X-PAYMENT` names are also accepted for backwards compatibility. If no payment header is present, the endpoint returns the 402 payment requirements. in: header name: PAYMENT-SIGNATURE required: false schema: example: eyJ4NDAyVmVyc2lvbiI6MiwicGF5bG9hZCI6Ii4uLiJ9 type: string requestBody: description: >- No JSON body required. Payment is sent via the X-402-Payment header. Send an empty POST to discover payment requirements. required: false content: application/json: schema: type: object properties: {} responses: '200': description: Top-up completed successfully. headers: PAYMENT-RESPONSE: description: >- Base64-encoded x402 v2 settlement result (`{ success, network, payer, transaction }`). schema: type: string content: application/json: schema: type: object properties: success: type: boolean enum: - true data: type: object properties: walletAddress: type: string description: Wallet that received the credited balance. example: 0xyour_wallet_address amountCredited: type: number description: Amount credited to the wallet in USD. example: 10 newBalance: type: number description: Updated wallet balance in USD after the top-up. example: 22.5 paymentId: type: string description: Unique identifier for the x402 payment. example: payment_01HZY8M4W4Y6QZ8B6Q4P0V3J2K required: - walletAddress - amountCredited - newBalance - paymentId additionalProperties: false required: - success - data additionalProperties: false '400': description: Invalid request parameters content: application/json: schema: type: object properties: error: type: string description: Machine-readable x402 error code. example: X402_INVALID_PAYMENT message: type: string description: Human-readable description of the x402 failure. example: Invalid payment header details: type: object properties: {} description: Optional structured details about the x402 error. example: reason: signature_mismatch required: - error - message additionalProperties: false '402': description: Payment information required before the top-up can be processed. content: application/json: schema: type: object properties: x402Version: type: number description: x402 protocol version. example: 2 accepts: type: array items: type: object properties: scheme: type: string enum: - exact description: x402 payment scheme. example: exact network: type: string description: >- Payment network in CAIP-2 form (e.g. `eip155:8453` for Base, `solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp` for Solana mainnet). example: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp amount: type: string description: >- Minimum payment amount in base units (USDC has 6 decimals). example: '5000000' asset: type: string description: USDC token address or mint for the selected network. example: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v payTo: type: string description: Receiver wallet address. example: 8qUL23aSj7mDWdoLMXGHFvnVCT9wd7jXcysiekroADEL maxTimeoutSeconds: type: number description: >- Maximum time allowed for payment settlement, in seconds. example: 300 extra: type: object properties: {} description: >- Network-specific x402 metadata. Solana accepts include a feePayer. example: name: USD Coin version: '2' feePayer: BFK9TLC3edb13K6v4YyH3DwPb5DSUpkWvb7XnqCL9b4F required: - scheme - network - amount - asset - payTo - maxTimeoutSeconds additionalProperties: false description: Array of accepted payment options. required: - x402Version - accepts additionalProperties: false '429': description: Rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/StandardError' '500': description: An unknown error occurred content: application/json: schema: type: object properties: error: type: string description: Machine-readable x402 error code. example: X402_INVALID_PAYMENT message: type: string description: Human-readable description of the x402 failure. example: Invalid payment header details: type: object properties: {} description: Optional structured details about the x402 error. example: reason: signature_mismatch required: - error - message additionalProperties: false security: [] components: schemas: StandardError: type: object properties: error: type: string description: A description of the error required: - error securitySchemes: BearerAuth: bearerFormat: JWT scheme: bearer type: http ````